Conventional heavy oil degreaser compositions contain so-called "alkaline builders." Moreover, many heavy oil remover compositions include halogens which are undesirable for steel process equipment degreasers, because the halogens may contribute to stress cracking of the metal. Many heavy oil degreasers only work at full strength, and are ineffective when diluted by residual liquids contained within the process equipment being cleaned. Some heavy oil degreasers are ineffective at ambient temperatures and must be heated along with the process equipment in order to remove the heavy oil sludge. Conventional heavy oil removers generally are incapable of absorbing and/or neutralizing the toxic gases and vapors which have accumulated within fouled process equipment. Finally, many of the heavy oil remover compositions of the prior art are toxic and not biodegradable.
Moreover, conventional heavy oil remover compositions are not useful for dissolving and removing heavy oils that have a high wax content. When conventional heavy oil remover formulations are used to clean process equipment containing high wax content heavy oil sludges, it is observed that such formulations are incapable of dissolving many of the waxes in the sludge. Also, those materials which are dissolved do not easily self-demulsify when mixed petroleum waxes are present. This is particularly inconvenient since demulsification is essential to the recovery of useful petroleum products from a sludge cleaning process. Finally, high wax content petroleum sludges typically invert, changing from a liquid phase at ambient temperatures to a solid at conventional sludge cleaning temperatures in the range of 80 degrees Celsius and higher. Since these higher cleaning temperatures are required in conventional cleaning processes in order to dissolve and emulsify the largest carbon chain length and highest melting point waxes, this phenomenon of congealing at higher temperatures tends to diminish the ability of conventional heavy oil remover formulations to extract and recover the oils and waxes from high wax content heavy oil sludges.
Waxes are defined as substances that are plastic solids at ambient temperatures and, on being subjected to moderately elevated temperatures, become low viscosity liquids. One type of wax "Paraffin Wax" is a petroleum wax which occurs naturally in many types of crude oil around the world. Chemically, paraffins, and by extension paraffin waxes occurring naturally in petroleum, are usually mixtures of straight carbon chain alkanes. The physical properties of the paraffin waxes, including melting point, congealing point, and plastic flow properties, vary with the "carbon chain length" of the wax or waxes present in the petroleum. When combined with the presence of other types of petroleum hydrocarbons found in natural petroleum sources, the physical properties exhibited by wax impurities in natural petroleum can produce difficulties with storage tanks and other process equipment, leading to a buildup of difficult to remove sludges with a mixed wax and petroleum impurities content. These waxes eventually cause a reduction in tank storage and equipment processing capacity as they build up, and also present a difficult cleanup problem as they are by their chemistry not soluble in most solvents.
U.S. Pat. No. 5,085,710 to Goss discloses a composition for removing oil sludges utilizing an alkylphenol adduct and a castor oil etholylate. U.S. Pat. No. 5,389,156 to Mehta et al discloses a heavy oil degreaser including a terpene and a second nonionic co-surfactant from the family of ethylene oxide/propylene oxide polyol adducts. These disclosed formulations are not effective for dissolving high wax content heavy oils, and additionally suffer from a number of the undesirable characteristics listed above.
It would be desirable to prepare a high wax content heavy oil remover composition that is effective for dissolving and emulsifying high wax content heavy oil sludges, and which is additionally free from alkaline builders and halogens, capable of absorbing toxic gases and vapors such as hydrogen sulfide and benzene, nontoxic, and biodegradable.